Goodwill and Other Intangible Assets - Changes in Carrying Value of Goodwill by Reportable Segment (Parenthetical) (Details) - USD ($) $ in Millions		Mar. 31, 2022	Dec. 31, 2021
Goodwill [Roll Forward]
Goodwill	[1]	$ 1,710.0	$ 1,722.2
Jefferson Wells
Goodwill [Roll Forward]
Goodwill		55.5
Right Management
Goodwill [Roll Forward]
Goodwill		62.1
France
Goodwill [Roll Forward]
Goodwill		66.4	68.2
Americas | United States
Goodwill [Roll Forward]
Goodwill		1,013.0	1,013.0
Americas | United States | Jefferson Wells
Goodwill [Roll Forward]
Goodwill		1,091.7	1,091.7
Southern Europe | France
Goodwill [Roll Forward]
Goodwill		72.5	74.3
Southern Europe | Italy
Goodwill [Roll Forward]
Goodwill		$ 3.8	$ 3.9

[1] Balances were net of accumulated impairment loss of $644.2 as of both March 31, 2022 and December 31, 2021.